Set boundaries to mouse rotation behaviour.

Hello guys, how do i set this script to have a minimum and a maximum value of change? Any ideas here? Thank you all.

Script:

 //cannon rotation
 var verticalSpeed : float = 2.0;
 function Update () {
     //Mouse delta (this value is not between -1 and 1)
     var v : float = verticalSpeed * Input.GetAxis ("Mouse X");
     //Debug.Log(Input.GetAxis("Mouse X"));
     transform.Rotate (0, 0, v);
 }